First video of bird pollination in Astroloma stomarrhena

I’m thrilled to share this never-before seen sequence of birds feeding on Astroloma stomarrhena, a winter-flowering shrub endemic to Western Australia.

Earlier this year, I decided A. stomarrhena looked like a perfect candidate for my new study on pollinators and gene flow. What I needed was a bird-pollinated species of plant, closely related to an insect-pollinated species. This one seemed to match all the criteria I needed, except there was no evidence that it was bird-pollinated. But with those long, tapered corolla tubes, and that pink-red coloration, I believed that birds absolutely had to be the pollinator.

The danger was, that while birds might be visitors, the plant could be somewhat “generalized”, and also use insects. This is pretty common, especially in places like Australia where European Honeybees (Apis mellifera) have invaded ecosystems that evolved in their absence, and honeybees will visit absolutely everything whether the plants are adapted to bees or not.

By deploying a new camera-trapping method that I am developing to record insect visitation, I was able to gather several days of pollinator observations, despite some very bad weather. After initially being baffled as to what honeyeater might visit such a low ground-hugging shrub, I got my answer after day one, when I captured video of my new favourite bird: the Tawny-crowned Honeyeater (Gliciphila melanops) feeding on the flowers. Furthermore, the recordings of honeybee fly-bys are sufficient to rule them out as pollinators.

This little result is a win on two fronts: a successful trial of new pollinator-monitoring cameras, and vindication of predicting pollinators from flower morphology.

Click here for the full HD video.

0ativxJ - Imgur

Advertisements

New paper: Unearthing diversity in fungal dark matter

To be born an orchid is a most unlikely thing. First your parents must be pollinated, which is difficult. Orchids are both rare, and rarely pollinated due to the bizarre and dishonest means by which they go about attracting pollinators. Added to that, orchids often rely on a single species of pollinator to do the job.

Let’s say, however, that your orchid parents do manage to achieve fertilization. Your orchid mother will produce many thousands of tiny dust-like seed, which will be jettisoned into the wind. Unlike most seeds, you have no maternal energy investment to power your germination and first days as a seedling. Instead, you must rely on blind luck to land you within reaching distance of a strand of soil fungus. This fungus is the wet nurse to bring you into the world, invading the seed coat and hooking the young orchid up to a network of fungal strands that pervade the soil. Tapping into this network provides you with the first sips of carbohydrate and nutrient you need in order to build your first green leaf and begin to stand on your own roots. But it is not enough to land near any fungus. Many orchid species require fungal partnership with a specific species of fungus for this to occur at all. Multiplied together, it is a wonder that orchids ever overcome these odds to propagate themselves into the next generation.

The southwest of Western Australia is rightly famous as a global biodiversity hotspot. The area is particularly rich in orchids, and the spider orchids (Caladenia) are some of the most impressive and diverse of the region’s main orchid groups. In 1967, University of Adelaide researcher John Warcup discovered in association with Caladenia a new genus of fungi. Today those fungi are called Serendipita, and although we have known of them for around 60 years, there have been less than a handful of species discovered and described.

img_0174

The spider orchid Caladenia arenicola was one of those sampled in the study

img_0494-1

White spider orchid (Caladenia splendens)

Ubiquitous yet invisible

Although related to mushrooms, Serendipita fungi have not been observed producing the conspicuous spore-bearing fruit bodies we usually use to find and identify them. This makes them largely invisible, and I have therefore never observed them in the wild. Despite that, recent research using DNA sequencing has found them to be absolutely everywhere. Inside all kinds of plants, outside all kinds of plants, and distributed from the equator to Antarctica. It is clear then that there must be a hidden biodiversity of these species siting, waiting to be discovered.

My study took a wide sample of southwest WA spider orchid samples and assayed them for the presence of Serendipita fungi. We then sequenced the DNA of all the fungi we found, and used a new analytical technique for dividing that DNA sequence diversity into units that are probably species. This is currently the only way to sensibly identify Serendipita fungi, as they all look completely alike and do not produce spores in the lab.

We found a total of eight species of Serendipita fungi, including the original species discovered by Warcup back in the 60s. These came from a total of 18 species of orchid. At some sites where we sampled multiple orchid species, we found six species of Serendipita, meaning that the fungi were as diverse as the orchids!

img_0970-1

Lying just below the soil horizon, that swollen, yellow stem bit is called the “collar”, and its where all spider orchids keep their fungus.

Untapped agricultural potential?

Although we have chosen to study these Serendipita in association with orchids, their wide host association has got other researchers interested in their role in plant health and application to agriculture. For example, Warcup’s species and one other have been used in experiments (and patent applications) showing inoculation with Serendipita results in profound benefits for the host plant, including:

  • Increased plant weight in maize, poplar, parsley, tobacco, barley, wheat, switchgrass and Arabidopsis
  • Enhanced grain yield in barley
  • Accelerated plant development in barley
  • Greater seed set, increased growth and faster flowering time in tobacco
  • Increased wheat yield in poor soils
  • Improved nutrient uptake in chickpea and lentil
  • Improved salinity tolerance in barley
  • Enhanced protection against root and stem pathogens in barley
  • Improved resistance to stem pathogens in tomato
  • Stronger defense response against mildew leaf pathogen in barley
  • Increased essential oil content in fennel and thyme
raycraven-sebacina-worldjmicro-2016

Figure 7 from Ray and Craven (2016): Root growth in winter wheat in Serendipita vermifera inoculated plants (left) versus control (right)

These proven benefits make Serendipita a potentially powerful tool to enhance plant productivity and stress tolerance in crops. Furthermore, application of Serendipita fungi could be an organic alternative permitting growers to lower the application of unsustainable and ecologically harmful synthetic fertilizers. Our knowledge of plant-Serendipita associations in the wild suggests that these relationships are more prevalent in nutrient poor soils such as those in southwest WA. They are probably one factor that allows our plant diversity to thrive in such weathered, poor soils. This means that species of fungi that have evolved with the nutrient poor soils (like those discovered in this paper) might be untapped tools to enhance agriculture taking place in those very same soils.

 

(Erratum: This story was edited to replace the figure attributed to Ray and Craven (2016). The first image I used was one showing Arabidopsis capability for mycorrhizal association. Arabidopsis is typically thought to be a non-mycorrhizal plant, which is why this is interesting. The image however showed slower growth in the mycorrhizal treatment. A related Serendipita has been shown to enhance root growth in Arabidopsis however. I have now updated the post with a more appropriate image of root growth gains in wheat. Thanks to Pawel Waryszak (@PWaryszak) for pointing this out.)

 

My study:

Whitehead, M. R., Catullo, R. A., Ruibal, M., Dixon, K. W., Peakall, R., & Linde, C. C. (2017). Evaluating multilocus Bayesian species delimitation for discovery of cryptic mycorrhizal diversity. Fungal Ecology, 26, 74-84.

Further reading:

Weiß, M., Sýkorová, Z., Garnica, S., Riess, K., Martos, F., Krause, C., … & Redecker, D. (2011). Sebacinales everywhere: previously overlooked ubiquitous fungal endophytes. Plos one, 6(2), e16793.

Weiß, M., Waller, F., Zuccaro, A., & Selosse, M. A. (2016). Sebacinales–one thousand and one interactions with land plants. New Phytologist, 211(1), 20-40.

Ray, P., & Craven, K. D. (2016). Sebacinavermifera: a unique root symbiont with vast agronomic potential. World Journal of Microbiology and Biotechnology, 32(1), 16.

Bokati, D., & Craven, K. D. (2016). The cryptic Sebacinales: An obscure but ubiquitous group of root symbionts comes to light. Fungal Ecology, 22, 115-119.

Photos from the field: East Gippsland, Victoria

I recently began a brand new project with the University of Melbourne. The beginning of a new project is filled with equal parts excitement and trepidation—excitement at the novelty, the blank canvas, the potential, and trepidation at not wanting to put a foot wrong in critical early decisions that will affect the outcome of a career-defining opportunity.

Here the photos from a first foray into East Gippsland, surveying sites for bird-pollinated Prostanthera walteri.

img_2600

Mt. Elizabeth

 

img_2604

img_2610

Snowy River National Park

img_2659

Prostanthera walteri

img_2543

Prostanthera hirtula

img_2613

McKillops Bridge

img_2614

The Snowy River

img_2616

The Snowy River

img_2623

Prostanthera walteri

img_2638

img_2626

Snowy River National Park

img_2645

Gippsland waratah – Telopea oreades

prostcomp1

Floral diversity in Prostanthera

 

Australia’s sexual swindlers.

Seduction. Pollination. Deception.

Screenshot 2016-09-30 09.37.47.png
I recently wrote an article for Wildlife Australia about Australian sexually deceptive orchids, their evolutionary biology, and historical and current research about them. You can download and read the article here: PDF. Thanks to Carol Booth for her collaboration and editorial guidance.

The latest of Australia’s sexually deceptive orchids that I have seen (below) are Caleana major, the Flying Duck orchid (left), and a spider orchid Caladenia clavigera (right). Both were photographed last week in Brisbane Ranges NP, Victoria.

Flowering this year is one of the best seasons of recent times both east and west of the country. So if you’re in Australia, don’t miss the chance to get out bush and enjoy it.

Sex, Lies and Nectar: Evolutionary Biology as Written by Flowers

I spoke to the Canberra Skeptics group earlier this week, on a subject most near to my heart. The abstract appears below. It is my aim to soon turn elements of this into a video for online audiences.

In the eyes of evolution, finding a suitable mate for reproduction is one of the most critical stages in any organism’s life. The great majority of flowering plants have outsourced this essential service to animals, giving rise to a fascinating evolutionary dance between plants and pollinators.

Charles Darwin was the first to recognize that flowers were superb teachers of evolution. I will touch on his classic work and explain what we have since learned about remarkable flowers who smell like dung and death, flowers who attract insects with the false promise of sex and a fly with a ridiculously long tongue.

These and other awesome examples of floral evolution would surely have thrilled Darwin, and may even solve his “abominable mystery”: the rapid rise of the spectacular diversity of flowering plants.

IMG_0850-3

Male thynnid wasp gripping tightly to the lure of the hammer orchid (Drakaea glyptodon).

Pollination, evolution and an orchid’s seductive ruse.

In a PR coup for dumpy little green orchids everywhere, research from my PhD recently landed on the cover of the journal Evolution. But what is it about?

Spring. The Blue Mountains, west of Sydney. Altitude 1000m. Frosty winds whip a swaying eucalypt canopy infiltrated by billowing cloud. Down below, amongst snowgrass tufts, rotting logs and bracken dwell the diminutive bird orchids. Genus: Chiloglottis. They huddle in tight colonies, sporadically sprayed by the high country squall.

Each plant holds two leaves pressed flat to the damp ground. Between the leaves a stem rises, holding aloft a single intricate flower in dusky shades of green and burgundy. When banks of cloud give way to azure sky and the shrike-thrushes resume their piping, these small blooms become irresistible lures.

Their target are the gracile flower wasps. Slim glossy black insects, zooming silently on shimmering wings. They are helplessly drawn to the flower. The bird orchid is emitting a scent, detectable only to wasps, which signals the promise of a mate. Known as ‘sexual deception’, the elaborate ruse uses a precise mimicry of female wasp pheromones to fool male wasps into pollinating the orchid.

However, here on the forest floor there is not only one species of orchid outwitting wasps for its own reproductive ends. Look closer and slight differences in the characteristics of flowers and visiting wasps betray something more complex and interesting. There are actually two species here, looking largely the same, growing in the same places, both deceiving their wasp pollinators through the false promise of sex.

By emitting subtle variations of their chemical trickery, these orchids have “tuned in” to two different pollinator species. This research paper explores this phenomenon as a way of separating the gene pools of closely related organisms. At the heart of it, the story here is about the forces that keep species apart once they split, or reproductive isolation.

First, we show that the different pheromones emitted by the two orchids are responsible for attracting different pollinators. Through arcane powers of chemical synthesis that I do not understand, chemists created synthetic orchid pheromones for us. We took these into the landscape and showed that the two chemicals attract two different wasps. The only perceivable difference between the wasps involved is yellow spangles on the carapace of one of the varieties. What’s more, this specific attraction is exclusive. Chemical A only attracts wasp A, and chemical B only appeals to wasp B.

Next, we take real flowers of both kinds and place them in a row and watch the hapless wasps roll in. We see that wasp A is only attracted to flower A, even when flower B is present just centimetres away. The results are identical to the results of the synthetic pheromone experiment.

On the basis of scent, we therefore expect that orchid A may never mate with orchid B. Exclusive attraction ensures that despite living amongst one another, some orchids may never exchange genes. Despite looking almost the same to us, they may as well exist on separate islands. They distinct separate species.

In order to back this up we then looked at the genetics of the species. By using the same kind of genes used in human DNA fingerprinting we were able to show that the two kinds of orchid exhibit differences in their gene pools of a degree expected if they were different species. Furthermore, analysis showed not a single individual displaying the genetics of a hybrid. Our last tests were to make hand-pollinated hybrids to check that hybrids could indeed form. These crosses showed hybrid offspring germinated and grew faster than pure crosses.

The potential for animals to drive the formation of plant species has long been recognized. This study gives us a strong case study of how that process might look. Our orchids are spectacular examples of the power of pollinators to create and maintain plant species. Through selective pollinator attraction, the orchids have been set upon unique and separate evolutionary journeys.

Further reading:

Whitehead, M. R. and Peakall, R. (2014) Pollinator specificity drives strong prepollination reproductive isolation in sympatric sexually deceptive orchids. Evolution 68: 1561–1575. doi: 10.1111/evo.12382

Rod Peakall and Michael R. Whitehead (2014) Floral odour chemistry defines species boundaries and underpins strong reproductive isolation in sexually deceptive orchids Annals of Botany 113 (2): 341-355 first published online September 19, 2013 doi:10.1093/aob/mct199

Plant pollinator interactions in the South African flora

The slides from my recent departmental seminar at the ANU are below.

The first half of the talk concentrates on plant-pollinator interactions, floral guilds and floral evolution. The second half is a slideshow of vistas, creatures and plants I encountered in my work.

Roses reflect greatest above 620 nm, Violets reflect at 420 – 480 nm…

Roses are red,  Violets are blue,  Botany is sexy, But less so than you.

Roses are red,
Violets are blue,
Botany is sexy,
But less so than you.

Along with odour, flower colour is perhaps the most important cue plants use to advertise to pollinators. Change the colour of a flower and that change can have large consequences on which pollinating animals are likely to visit[1]. Bees, for example, are attracted to purple flowers with UV highlights. If that plant were to mutate to white, it could very well find itself being visited by nocturnal moths[2].

In studying plant-pollinator evolution and ecology, it is very important then that we have some objective quantification of the colour of a flower. Human eyes are famously fallible and many insects and birds can see outside the range of our colour vision (400 – 700 nm).

The instrument we use is a spectrometer[3]. It uses optic fibres to bounce an initially white-light beam off the surface you want to measure. The wavelengths of light that are reflected (as opposed to absorbed) determine the colour of the surface you are looking at. The spectrometer collects the reflected light, separates the wavelengths through diffraction and digitises the signal. The result is a graph such as the one above.

In the graph, the wavelength is given on the horizontal axis, while the proportion of reflectance is on the vertical. The rainbow bar above provides an approximation of how the human eye perceives a given wavelength of light. The rose therefore will reflect greatest at wavelengths above 620 nm, the red part of the spectrum. A violet most strongly reflects around 420 – 480 nm. A pure white surface would show high reflectance across the range of the visible light spectrum.

Dedicated to my sweetheart, who for the second year in a row has been alone on Valentine’s.

Kniphofia are red, Agapanthus are blue.

Fieldwork is fun, But I do miss you. 

My bruised human ego

IMG_1344-1

This is the best photo I got of a group of baboons who gave me quite an experience the other day.

On a sandy fynbos trail, I rounded a corner obscured by vegetation and came abruptly face to face with a troupe of seven of these creatures. The closest member was only 3 metres from me. All of them were stopped, standing or sitting,  looking at me as I did the same. My first reaction was one of awe, these creatures are impressively muscular and intimidating up close. One of them, a very large male, was wearing a radio collar. My second instinct was to take advantage of the photo opportunity, but my camera was in my backpack.

My only close experience with monkeys comes from Indonesian macaques, and extrapolating from the damage these ones wreak on tourists’ belongings I was not keen to get the baboons interested in anything I owned. I was also aware that some baboon troupes in the Cape have a reputation for raiding. Bins, bags, picnics, cars, houses are all fair game. They have overcome their fear of humans and are now a famous nuisance requiring full time management.

My bag therefore remained zipped and in place on my back. I raised my arms and hissed, to try and persuade them off the trail. One of the leaders began to advance on me, and the others stood up to follow suit.

Finally, I was forced to concede the path to the baboons. I back-stepped into the bush beside the track, allowing them a 2 metre thoroughfare which they calmly took in an orderly and nonchalant fashion. Only after passing me, when their backs were exposed, did they pick up speed into a quick trot for a dozen metres to put some distance between us.

 

Red Hill fynbos track

Kleinplaas Dam fynbos track

 

As you were, Australian researchers.

Waking up to look at this before a coffee and a shower was enough to put me into fight or flight mode this morning.

With hackles raised I read on and found a sciency corner of Australian Twitter users in a flap about Abbott’s 20% ARC cuts. #AbbottsRazor #ARCcuts etc etc

While the wording of these Tweets is strictly true, they are also completely misrepresenting the politics of these ARC funding estimates.

The numbers are below. The top row is the current budget handed down by Labour in 2013. The middle row is the Abbott Government amendment. The bottom row is the difference. Numbers represented in thousands (000’s).

2013-14

2014-15

2015-16

2016-17

TOTAL

May budget

$883,959

$879,983

$834,587

$788,710

$3,387,239

Amendment

$883,959

$853,110

$783,253

$716,205

$3,236,527

Difference

$0

$26,873

$51,334

$72,505

$150,712

YES. ARC funding will dive by 19% in the next 4 years. But this is a dive courtesy of the Labour Government’s May 2013 budget.

YES. Abbott is cutting funding further, but this amounts to 4% cut in total ARC spending over the next 4 years. The majority of the sliding investment trend came from the initial budget trajectory set out in May.

The time to make a flap about budget cuts was in May. And some of us had a good whinge then. The truth of this latest news is that it is a continuation of the prevailing “death by a thousand cuts” trend, as another shaving is whittled off our future investment in research and innovation.

But the big lesson here is to hold fire when it comes to social media. A forgiving person might acknowledge that this shows that scientists are only human, prone to the occasional passionate, emotional, reactionary outbursts. A harder judge might question whether researchers who don’t think critically and do a bit of their own “research”, deserve any ARC funding at all.

Thanks Alice Hutchings, for engaging your brain. And Tom Stayner for the title.

Postscript

Jeremy Shearman from the Genome Institute in Thailand has produced this graphic showing the effect of amendments on ARC funding over the last few years. The trend is one of providing more upfront dollars with increasingly steep sliding scales of less funding later.

ARC funding amendment history